In humans and animals, defects may form in tissues due to creation of a channel through a tissue wall or failure of a channel in a tissue wall to close. For example, the ductus arteriosus is a vessel connecting the pulmonary artery to the aorta in human and animal neonates, shunting blood flow around the developing lungs. The ductus arteriosus typically closes shortly after birth. However, in some individuals, the ductus arteriosus may stay open, leading to a defect known as patent ductus arteriosus (PDA). PDA may lead to clinical conditions such as cardiac arrhythmias, congestive heart failure, and pulmonary over-circulation. Other conditions or defects involving open tissue channels include patent foramen ovale, ventricular septal defects, and atrial septal defects. Previous attempts to seal these tissue defects have involved surgical ligation, an invasive procedure that may lead to complications.